1 OO Implementation for the LHCb Rich Niko Neufeld Dietrich Liko.
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Transcript of 1 OO Implementation for the LHCb Rich Niko Neufeld Dietrich Liko.
2
Introduction
Study of OO Implementation of a Reconstruction program
Based on Standalone Programby Roger Forty et al.
Present a comparison Review Object Oriented features
3
Objective
Results of the FORTRAN Physics Resources
To be better then FORTRAN Object Orientation
Modularity Interfaces
4
UML Process
Specification using UML Use cases
Development using UML case tool Rational Rose
Iterative Development Several internal iterations
UML
Unified Modeling
Language
by
Booch, Jacobson &
Rumbaugh
5
Program Specification
Technical Proposal LHCb Note FORTRAN Program
Summary with all information Partial capture in use cases
6
One page on physics
Cherenkov Effect Emission of Photons
Aerogel & Gas Radiator Reflection of Photons Observation of Photons
Quantum Efficiency Detector Geometry
7
One page on algorithm
Local Likelihood Global Likelihood
Very effective CPU intensive
Other Algorithm possible Average emission angle
8
Framework
OO Framework to implement reconstruction algorithms
Simulation also possible
Here the Global Likelihood will be implemented
Benchmark for usability
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Use Cases
Question a Physicist might ask ... to a particle ... to a pixel ...
Global Likelihood
ChanhLN
jjij
M
ii
N
jjj
111
lnln
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Use cases
MomentumTrue Particle Code
PhysicistEmitted Number of Photons
Expected Number Photons
Geometrical Efficiency
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Detector
Rich
Radiator
Reflector
Detector
SimplifiedUML
Class Diagram
Static relations of Classes
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Event Event
TrackPixel
TrackExtrapolation
TrackSegment
Photon
I should be called DetectorElement !
15
Lifetime
Present for all Events Rich, Radiator, Reflector, Detector
Present for one Event Tracks, TrackExtrapolations,
Pixel, Photons
Temporary Photon Spectrum, PixelID, Single Photon
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Pixelid
tube
RecPixelsignal
globalPositionlocalPosition
size
PhotonDetector
But I am smart!
• Example trivial
• expensive calculations
• context questions
The PhotonDetector does all the
work for me !
I am not so smart ...
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Standalone Program
Minimal Environment Contains its own Transient Event
Model Parameter Files Histograms from CLHEP
Only for this test!
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Optimisations
Since last presentation two weeks ago Program about a factor 2 slower
Profiling and Debugging Allocation of STL container operator[] Algorithmic improvements
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Technical Proposal
Rec True Pe K p X
e 6233 7 328 0.95 8 224 554 31 0.27 5 10 13114 1 8 0.99K 1 39 1083 11 0.96p 1 4 1 427 1 0.98X 3 8 197 27 3990 0.94 0.99 0.90 0.92 0.97 1.00 0.99
500 Events
B
background
“Clean”
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Results
Rec True Pe K p X
e 8848 7 426 3 51 0.95 20 230 1163 3 57 0.16 8 13 10891 9 29 0.99K 2 1 39 1083 11 0.97p 1 4 1 427 1 0.98X 154 2 67 12 9700 0.98 0.98 0.91 0.87 0.97 1.00 0.99
Difference in particle population, in particular for X particles:
Different sample, small differences in the modeling of the inner edges
Migration to Reduced Efficiency
Reduced Purity
500 Events
B
background
“Clean”
25
CPU Comparison
500 MhzPentium III
G77 7.52
G++ 8.32
Sec/E
vent
7 8 9
100 Events
B
Background
“Clean”
26
Kuck & Associates, Inc.
Commercial C++ compiler Standard compliant Templates Patented optimization techniques Precompiled headers http://www.kai.com
Time-locked trial version for RH6.1
27
CPU Comparison
500 MhzPentium III
G77 7.52
G++ 8.32
Sec/E
vent
7 8 9
KCC 7.32
100 Events
B
Background
“Clean”
28
Summary
Outlined the development process Show physics results Show CPU comparisons
Why an OO program should be better ?
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FORTRAN
REAL FUNCTION DIST(POS,DIR)
C A line is given by POS and DIS
REAL POS(3), DIR(3)
C Radiator wall is described by its z position
REAL ZPOS(2)
COMMON /RADIATOR/ ZPOS
DIST = ACOS(DIR(3),VMOD(DIR,3))*(ZPOS(2)-ZPOS(1))
END
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FORTRAN
Does what it should Math is simple Probably more complicated in praxis
walls not normal to z more then one radiator
Some variables which are interpreted in the context
But your program works soon!
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Sometimes later ... … you want to improve the program
More realistic tracks More realistic radiators
But assumptions are not isolated There will be other places which depend
on these variables
You have to find all uses of the variables In your program at n places In other people programs at
unknown places
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Object Based
Assume two classes present Plane Ray (can intersect with plane)
My program has ... class Algorithm dist method
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Object Basedclass Algorithm {
Plane Radiator[2];
virtual double dist(const Ray & track) const;
}
double Algorithm::dist(const Ray & track) const {
return Radiator[1].intersect(track) - Radiator[0].intersect(track);
}
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Object Based
More compact Probably more general Math is done by somebody else
But main critic remains
If you want to improve the program,you have to find ...
n places in your own program unknown places in other programs
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Object Orientedclass Track {
public:
virtual double dist() const;
virtual double intersect(const Plane & plane) const;
virtual double intersect(……) const;
private:
Radiator * radiator_;
}
class Radiator {
public:
virtual double dist(const Track & track) const;
}
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Sequence DiagramRadiatorTrack
dist
dist
intersect
intersect
return dist
return dist
SimplifiedUML Sequence
Diagram
dynamic relation of classes
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Object Oriented
If one changes the Radiator ... One place to do the modifications
If one changes the Track ... Another single place to do the change
Implementation is hidden behind the interface
No dependency on the implementation details
Visitor Pattern
39
Summarize
FORTRAN does the job difficult to maintain
Object Based C++ does the job probably better still difficult to maintain
Object Oriented C++ dependencies are reduced
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Our Program does not depend on ... Track implementation Pixel implementation General Detector Geometry Photon radiation process Mirror choice Type of Photon Detector Photon Detector Assembly Details Reconstruction Strategy …..
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Integration to GAUDI
Algorithm is interfaced Package is nearly ready Release next week
Detailed documentation from the Rose Model available
We plan to include some “hand written” documentation for the release
42
Future in GAUDI
Next steps … Detector Description Other Algorithms Photon Detector Implementation
Not addressed
Structure of a general LHCb reconstruction program